Anatomical accuracy of interactive and automated rigid registration between X-ray CT and FDG-PET

Summary

Aim: Comparison of anatomical accuracy of softwarebased interactive (IRR) and automated rigid registration (ARR) of separately acquired CT and FDG-PET data sets. Patients, methods: Independently acquired PET and helical CT data from 22 tumour patients were registered manually using the Syngo advanced Fusion VC20H tool. IRR was performed separately for the thorax and the abdomen using physiological FDG uptake in several organs as a reference. In addition, ARR was performed with the commercially available software tool Mirada 7D on all of the patients. For both methods, the distances between the representation of 53 malignant lesions on PET and CT were measured in X-, Y-, and Z-direction with reference to a common coordinate system (X-, Y-, Z-distances). Results: The percentage of lesions misregistered by less than 1.5 cm was in X-direction 91% for IRR and 89% for ARR; in Y-direction 85% and 68%; in Z-direction 72% and 51%, respectively. The average X-, Y- and Z-distances for IRR ranged from 0.58 ± 0.55 cm (X-direction) to 1.17 ± 1.66 cm (Z-direction). For ARR, the average X-, Y- and Z-distances varied between 0.66 ± 0.61 cm (X-direction) and 1.81 ± 1.37 cm (Z-direction). Mixed effects analysis of the absolute X-, Y- and Z-distances revealed a significantly better alignment for IRR compared to ARR in Z-direction (p <0.01). Lesion size and localization either in thorax or abdomen had no significant influence on the accuracy of registration. Conclusion: For the majority of malignant lesions, manual image registration with the possibility to separately align different body segments was more accurate than the automated approach. Current software for ARR does not reach the anatomical accuracy reported for PET/ CT hybrid scanners.

Zusammenfassung

Ziel: Vergleich zwischen interaktiver manueller und automatischer Software-basierter starrer Registrierung von 18F-Deoxyglukose-Positronenemissionstomographien (FDG-PET) und Röntgencomputertomographien (CT) des Körperstammes. Patienten, Methoden: Bei 22 onkologischen Patienten wurden innerhalb von vier Wochen eine Ganzkörper FDG-PET und ein Spiral-CT gemäß klinischen Standardprotokollen ohne Harmonisierung von Patientenpositionierung und -atmung aufgenommen. Die Bilddaten wurden manuell auf einer Syngo-Workstation fusioniert (IRR). Des Weiteren erfolgte ihre Registrierung mit der automatischen starren Registrierungssoftware Mirada Fusion 7D (ARR). Die Qualität der Fusion wurde durch Messung der Distanzen zwischen visuell bestimmten Läsionsmittelpunkten von 53 neoplastischen Foci in drei Raumebenen evaluiert. Ergebnisse: Eine Fehlregistrierung von weniger als 1,5 cm wurde bei 91% (X-Richtung), 85% (Y-Richtung) und 72% (Z-Richtung) der Läsionen für die IRR ermittelt. Die entsprechenden Häufigkeiten für ARR waren 89% (X-Richtung), 68% (Y-Richtung) und 51% (Z-Richtung). Die durchschnittliche Fehlregistrierung reichte für IRR von 0,58 ± 0,55 cm (X-Richtung) bis 1,17 ± 1,66 cm (Z-Richtung). Für ARR variierten die durchschnittlichen Abstände der Läsionen von 0,66 ± 0,61 cm (X-Richtung) bis 1,81 ± 1,37 cm (Z-Richtung). Die statistische Analyse ergab eine signifikant schlechtere Registrierung durch ARR in Z-Richtung. Die Lage und Größe der Läsionen hatte keinen signifikanten Einfluss auf das Ausmaß der Fehlregistrierung. Schlussfolgerung: IRR war anatomisch genauer als ARR. Beide Verfahren erreichen für klinische Routinebilddaten nicht die anatomische Genauigkeit, wie sie in der Literatur für die Registrierung durch PET/CT-Hybridkameras berichtet wurde.

Keywords

FDG- PET - CT - image fusion - registration

Schlüsselwörter

FDG- PET - CT - Bildfusion - Registrierung

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